Cell constitution and characteristics of human atherosclerotic plaques selectively removed by percutaneous atherectomy

Association of Desmin Gene Variant rs1058261 with Cardiovascular Disease, the TAMRISK Study

AIMS

Since desmin expression is diminished in vascular smooth muscle cells during reparative processes, we wanted to study whether a common intragenic single nucleotide polymorphism at nucleotide position 828 (rs1058261) of the DES gene associates with hypertension, cerebrovascular complications, and all cardiovascular events in the Tampere adult population cardiovascular risk (TAMRISK) study.

MATERIALS AND METHODS

A Finnish periodic health examination cohort of 336 subjects with diagnosed hypertension and 473 controls were analyzed. Samples were genotyped for polymorphism using TaqMan techniques. Prevalence of ischemic heart diseases, incidence of cerebrovascular diseases, and transient cerebral ischemic attacks (TIAs) were obtained by self-report and the National Hospital Discharge Registry (HILMO).

RESULTS

There was no association of any of the rs1058261 genotypes with hypertension at the age of 50. When the subjects were followed to the age of 60, after adjustment for gender and body mass index, subjects with the genotype CC had higher incidence of cerebrovascular events (cerebrovascular diseases and TIA) (4.1%) compared with the T allele (1.6%) (p = 0.046). In addition, those with CC genotype had a higher incidence of all combined cardiovascular events (12.8%) compared with subjects with the T allele (8.5%) (p = 0.028).

CONCLUSIONS

Our findings suggest that variations in the DES gene may be involved in cardiovascular disease.

Cordyceps bassiana inhibits smooth muscle cell proliferation via the ERK1/2 MAPK signaling pathway

Cordyceps belongs to a genus of acormycete fungi and is known to exhibit various pharmacological effects. The aim of this study was to investigate the effect of Cordyceps species on the proliferation of vascular smooth muscle cells (VSMC) and their underlying molecular mechanism. A cell proliferation assay showed that Cordyceps bassiana ethanol extract (CBEE) significantly inhibited VSMC proliferation. In addition, neointimal formation was significantly reduced by treatment with CBEE in the carotid artery of balloon-injured rats. We also investigated the effects of CBEE on the extracellular signal-regulated kinase (ERK) signal pathway. Western blot analysis revealed increased ERK 1/2 phosphorylation in VSMCs treated with CBEE. Pretreatment with U0126 completely abrogated CBEE-induced ERK 1/2 phosphorylation. In conclusion, CBEE exhibited anti-proliferative properties that affected VSMCs through the ERK1/2 MAPK signaling pathway. Our data may elucidate the inhibitory mechanism of this natural product.

Characterization of a human 12/15-lipoxygenase promoter variant associated with atherosclerosis identifies vimentin as a promoter binding protein

Background

Sequence variation in the human 12/15 lipoxygenase (ALOX15) has been associated with atherosclerotic disease. We functionally characterized an ALOX15 promoter polymorphism, rs2255888, previously associated with carotid plaque burden.

Methodology/Principal Findings

We demonstrate specific in vitro and in vivo binding of the cytoskeletal protein, vimentin, to the ALOX15 promoter. We show that the two promoter haplotypes carrying alternate alleles at rs2255888 exhibit significant differences in promoter activity by luciferase reporter assay in two cell lines. Differences in in-vitro vimentin-binding to and formation of DNA secondary structures in the polymorphic promoter sequence are also detected by electrophoretic mobility shift assay and biophysical analysis, respectively. We show regulation of ALOX15 protein by vimentin.

Conclusions/Significance

This study suggests that vimentin binds the ALOX15 promoter and regulates its promoter activity and protein expression. Sequence variation that results in changes in DNA conformation and vimentin binding to the promoter may be relevant to ALOX15 gene regulation.

Proteomic analysis of human macrophages exposed to hypochlorite-oxidized low-density lipoprotein

The invasion of monocytes through the endothelial wall of arteries and their transformation from macrophage into form cells has been implicated as a critical initiating event in atherogenesis. Human THP-1 monocytic cells can be induced to differentiate into macrophages by phorbol myristate acetate (PMA) treatment, and can be converted into foam cells by exposure to oxidized low-density lipoprotein (oxLDL). To identify proteins potentially involved in atherosclerotic processes, we performed a proteomic analysis of THP-1 macrophages exposed to oxLDL generated by treatment with native LDL with hypochlorous acid/hypochlorite (HOCl/OCl(-)). We detected more than a thousand proteins, of which 104 differentially expressed proteins were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) and the NCBI database. The largest differences in expression were observed for bifunctional purine biosynthesis protein, vacuolar protein sorting 33A, breast carcinoma amplified sequence, adenine phosphoribosyltransferase, and tropomyosin alpha 3 chain. Interestingly, many apoptotic proteins such as lamin B1, poly (ADP-ribose) polymerase, Bcl-2 related protein A1 and vimentin were identified by MALDI-TOF analysis. Identities were confirmed by matching the sequence of several tryptic peptides using MALDI-TOF/TOF MS, Western blot analyses and immunofluorescent microscopy. The data described here will contribute to establishing a functional profile of the human macrophage proteome. Furthermore, the proteins identified in this study are attractive candidates for further biomarkers involved in the pathogenesis of atherosclerosis.

Differential display fingerprints: new approach to characterize smooth muscle cells and human coronary atherectomy tissues

AIM OF THE STUDY

Smooth muscle cells build up the normal media and stabilize atherosclerotic lesions whereas an inflammatory component is determinant for unstable angina. Smooth muscle cells, currently identified by alpha-actin, present a phenotypic heterogeneity and alpha-actin can be reduced in pathology. We tried to characterize vascular cell types, particularly smooth muscle cells, and coronary atherosclerotic tissues, by random genes expression fingerprints.

MATERIALS AND METHODS

Expression fingerprints (cDNA electrophoresis) were performed by differential display reverse transcriptase-polymerase chain reaction. Variability of fingerprints was studied for a panel of arterial muscle cell phenotypes and comparisons were made with fingerprints from other cell types (endothelial cells and macrophages). The technique was then applied to human coronary atherectomy samples compared to control human arterial (mammary) smooth muscle.

RESULTS

Arterial smooth muscle cells fingerprints were overall similar whatever the cell phenotype (native contractile, dedifferentiated in culture or epithelioid). Moreover, with two primer pairs, the muscular fingerprints markedly differed from the endothelial and the monocytic fingerprints. Application of differential display to coronary atherectomy samples was feasible. Interestingly, the pathological tissues exhibited either smooth muscle-like or smooth muscle-divergent fingerprints.

CONCLUSIONS

Smooth muscle cells and inflammatory cells exhibited distinct differential display fingerprint patterns. Thus, a simple expression profile of arbitrary genes provides a molecular bar code tool (pattern signature) useful to characterize vascular cell cultures or tissues. The present work proposes a method to analyze coronary atherectomy samples which estimates their whole quality, muscular versus non muscular (inflammatory), this is of interest for clinical research.

Edge restenosis: impact of low dose irradiation on cell proliferation and ICAM-1 expression

BACKGROUND

Low dose irradiation (LDI) of uninjured segments is the consequence of the suggestion of many authors to extend the irradiation area in vascular brachytherapy to minimize the edge effect. Atherosclerosis is a general disease and the uninjured segment close to the intervention area is often atherosclerotic as well, consisting of neointimal smooth muscle cells (SMC) and quiescent monocytes (MC). The current study imitates this complex situation in vitro and investigates the effect of LDI on proliferation of SMC and expression of intercellular adhesion molecule-1 (ICAM-1) in MC.

METHODS

Plaque tissue from advanced primary stenosing lesions of human coronary arteries (9 patients, age: 61 +/- 7 years) was extracted by local or extensive thrombendarterectomy. SMC were isolated and identified by positive reaction with smooth muscle alpha-actin. MC were isolated from buffy coat leukocytes using the MACS cell isolation kit. For identification of MC flow-cytometry analysis of FITC-conjugated CD68 and CD14 (FACScan) was applied. SMC and MC were irradiated using megavoltage photon irradiation (CLINAC2300 C/D, VARIAN, USA) of 6 mV at a focus-surface distance of 100 cm and a dose rate of 6 Gy min-1 with single doses of 1 Gy, 4 Gy, and 10 Gy. The effect on proliferation of SMC was analysed at day 10, 15, and 20. Secondly, total RNA of MC was isolated 1 h, 2 h, 3 h, and 4 h after irradiation and 5 microg of RNA was used in standard Northern blot analysis with ICAM-1 cDNA-probes.

RESULTS

Both inhibitory and stimulatory effects were detected after irradiation of SMC with a dose of 1 Gy. At day 10 and 15 a significant antiproliferative effect was found; at day 20 after irradiation cell proliferation was significantly stimulated. Irradiation with 4 Gy and 10 Gy caused dose dependent inhibitory effects at day 10, 15, and 20. Expression of ICAM-1 in human MC was neihter inhibited nor stimulated by LDI.

CONCLUSION

Thus, the stimulatory effect of LDI on SMC proliferation at day 20 days after irradiation may be the in vitro equivalent of a beginning edge effect. Extending the irradiation area in vascular brachytherapy in vivo may therefore merely postpone and not inhibit the edge effect. The data do not indicate that expression of ICAM-1 in quiescent MC is involved in the process.

Identification, structural, and functional characterization of a new early gene (6A3-5, 7 kb): implication in the proliferation and differentiation of smooth muscle cells

Arterial smooth muscle cells (SMCs) play a major role in atherosclerosis and restenosis. Differential display was used to compare transcription profiles of synthetic SMCs to proliferating rat cultured SMC line. An isolated cDNA band (6A3-5) was shown by northern (7 kb) to be upregulated in the proliferating cell line. A rat tissue northern showed differential expression of this gene in different tissues. Using 5' RACE and screening of a rat brain library, part of the cDNA was cloned and sequenced (5.4 kb). Sequence searches showed important similarities with a new family of transcription factors, bearing ARID motifs. A polyclonal antibody was raised and showed a protein band of 175 kd, which is localized intracellularly. We also showed that 6A3-5 is upregulated in dedifferentiated SMC (P9) in comparison to contractile SMC ex vivo (P0). This work describes cloning, structural, and functional characterization of a new early gene involved in SMC phenotype modulation.

Pathophysiological effects of radiation on atherosclerosis development and progression, and the incidence of cardiovascular complications

Radiation therapy while important in the management of several diseases, is implicated in the causation of atherosclerosis and other cardiovascular complications. Cancer and atherosclerosis go through the same stages of initiation, promotion, and complication, beginning with a mutation in a single cell. Clinical observations before the 1960s lead to the belief that the heart is relatively resistant to the doses of radiation used in radiotherapy. Subsequently, it was discovered that the heart is sensitive to radiation and many cardiac structures may be damaged by radiation exposure. A significantly higher risk of death due to ischemic heart disease has been reported for patients treated with radiation for Hodgkin's disease and breast cancer. Certain cytokines and growth factors, such as TGF-beta1 and IL-1 beta, may stimulate radiation-induced endothelial proliferation, fibroblast proliferation, collagen deposition, and fibrosis leading to advanced lesions of atherosclerosis. The treatment for radiation-induced ischemic heart disease includes conventional pharmacological therapy, balloon angioplasty, and bypass surgery. Endovascular irradiation has been shown to be effective in reducing restenosis-like response to balloon-catheter injury in animal models. Caution must be exercised when radiation therapy is combined with doxorubicin because there appears to be a synergistic toxic effect on the myocardium. Damage to endothelial cells is a central event in the pathogenesis of damage to the coronary arteries. Certain growth factors that interfere with the apoptotic pathway may provide new therapeutic strategies for reducing the risk of radiation-induced damage to the heart. Exposure to low level occupational or environmental radiation appears to pose no undue risk of atherosclerosis development or cardiovascular mortality. But, other radiation-induced processes such as the bystander effects, abscopal effects, hormesis, and individual variations in radiosensitivity may be important in certain circumstances.

Subnormal shear stress-induced intimal thickening requires medial smooth muscle cell proliferation and migration

Arterial intimal thickening is consisted of predominately smooth muscle cells (SMC). The source of these SMCs and mechanisms response for their changes have not been well cleared. Using a model of rabbit common carotid artery (CCA) shear induced intimal thickening, we sought to identify and describe the source of SMCs in intima. The enlarged CCA 28 days after arteriovenous fistula (AVF) creation was subjected to subnormal wall shear stress (WSS) for 1, 3, and 7 days by closure of the AVF. To determine SMC proliferation, BrdU pulse labeling of SMCs was performed. BrdU-labeled SMCs were tracked over time to further confirm SMC migration. In response to subnormal WSS intimal thickening developed progressively. BrdU-labeled SMCs localized in the subendothelial area. When the BrdU-labeled medial SMCs were tracked 1 day after AVF closure, progenies of these BrdU-incorporated SMCs increased by 4.8-fold with 75% of them in the intima. They were 12-fold increased with 83% in the intima 7 days after. En face examination showed an accumulation of SMCs in internal elastic lamina gap after AVF closure, which later migrated into subendothelial area. In situ hybridization revealed increased TGF-beta1 mRNA expression in intimal SMCs. This study demonstrates that the medial SMCs are the predominant cells in subnormal WSS-induced intimal thickening. Early expression of TGF-beta1 may play an important role in the process of intimal thickening.

Using CCM and DHPLC to detect mutations in the glucocorticoid receptor in atherosclerosis: a comparison

Growing evidence suggests that restenosis may be caused by a failure in growth inhibitory and apoptotic systems that would normally mediate lesion regression. One such inhibitory system is the glucocorticoid receptor. This paper develops, assesses and compares chemical cleavage of mismatch (CCM) and denaturing high-performance liquid chromatography (DHPLC) for their utility in detecting mutations in this system. The results of the two methods correlated in 74% of cases in a cohort of endarterectomy patients studied by these two methods.

Effects of local delivery of trapidil on neointima formation in a rabbit angioplasty model

1. Smooth muscle cell (SMC) proliferation can result in luminal reduction of a vessel following balloon angioplasty. This study was designed (i) to determine if local administration of trapidil (triazolopyrimidine) into a vessel wall reduces neointima formation, and (ii) to explore the mechanism involved in the subsequent reduction in cell proliferation. 2. Following balloon angioplasty in 40 anaesthetized New Zealand White rabbits, trapidil (50-200 mg) or its vehicle (saline) was injected into the dilated vessel wall of the right femoral artery. Experimental groups and time of investigation: (I) vehicle (2 weeks, n = 3), (II) trapidil-100 mg (2 weeks, n = 3), (III) vehicle (3 weeks, n = 8), (IV) trapidil-50 mg (3 weeks, n = 5); (V) trapidil-100 mg (3 weeks, n = 9) or (V) trapidil-200 mg (3 weeks, n = 7). 3. After 2 weeks, there was a significant reduction of intimal hyperplasia (expressed as intima to media area ratio) in the trapidil group compared with vehicle (0.44 +/- 0.04 vs 0.93 +/- 0.04, *P < 0.05) and also a significant reduction in cell proliferation (% ratio of BrdU-positive cells to total cell number: vehicle 14 +/- 2% vs trapidil 6 +/- 1%, *P < 0.05). 4. After 3 weeks, there was a dose-dependent reduction of intimal hyperplasia in the trapidil groups compared with vehicle (trapidil 50 mg 1.14 +/- 0.04; trapidil 100 mg 0.91 +/- 0.09*; trapidil 200 mg 0.77 +/- 0.09* vs vehicle 1.67 +/- 0.23, *P < 0.05). 5. Thus, the local administration of trapidil to the rabbit femoral artery reduces the neointima formation, which occurs 2 or 3 weeks after balloon angioplasty via a mechanism, which is dependent on inhibition of cell proliferation.

The binding in vitro of modified LDL to the intermediate filament protein vimentin

Membrane-associated proteins with specific binding properties to modified LDL were investigated in J774 macrophages and Mono Mac 6 sr cells. Ligand blotting of membrane proteins revealed a 54-kDa protein which bound oxidized and acetylated but not native LDL. The 54-kDa protein, isolated by 2D-PAGE, was identified as vimentin. (125)I-AcLDL bound to purified vimentin and desmin in a saturable manner, with an approximate K(d) of 1.7 x 10(-7) M (89 microgram/ml) and 8.0 x 10(-8) M (41 microgram/ml), respectively. Blots of vimentin mutant proteins with deletions in the positively charged N-terminal head domain showed that amino acids 26-39 are essential for the binding of AcLDL by vimentin. Taken together, our data indicate that vimentin binds modified LDL, but not native LDL, in a specific and saturable manner. Vimentin filaments extend throughout the cytoplasm as far as the inner surfaces of plasma and vesicular membranes. Vimentin may thus play a role in membrane-associated steps involved in the intracellular processing of oxidized LDL, contributing to its unregulated uptake and intracellular retention by cells of the atherogenic plaque.

Identification and cloning of a new gene (2A3-2), homologous to human translational elongation factor, upregulated in a proliferating rat smooth muscle cell line and in carotid hyperplasia

Smooth muscle cells (SMCs), before migration and proliferation in the intima of the vessel wall, change from a normal contractile to a pathological proliferating phenotype. The molecular regulatory mechanisms implicated in such phenotypic changes remain poorly understood. In this study, using differential display, we have isolated for the first time a new gene (2A3-2) that is overexpressed in a rapidly proliferating, but not synthetic, rat SMC line. This was further confirmed by northern blot performed on the 2 cell types. Moreover, balloon catheter injury of rat carotids showed, by a virtual northern technique, an upregulation of this new gene in hyperplasia vessels. This new gene (2A3-2, 1.2 kb) was present in skeletal muscle, heart, aorta, lung, liver, kidney, and spleen. In addition, 5' rapid amplification of cDNA ends (5' RACE) allowed the cloning and sequencing of this 1.2-kb gene. Comparison of this newly identified gene sequence with data banks showed a strong homology to human and bovine mitochondrial translational elongation factor. The 2A3-2 gene, identified in this study, may play a vital role in the cascade of events implicated in switching SMC phenotype from a quiescent to a proliferate one.

Glucocorticoid resistance caused by reduced expression of the glucocorticoid receptor in cells from human vascular lesions

Mechanisms that control the balance between cell proliferation and death are important in the development of vascular lesions. Rat primary smooth muscle cells were 80% inhibited by low microgram doses of hydrocortisone (HC) and 50% inhibited by nanogram concentrations of transforming growth factor-beta1 (TGF-beta1), although some lines acquired resistance in late passage. However, comparable doses of HC, or TGF-beta1, failed to inhibit most human lesion-derived cell (LDC) lines. In sensitive LDC, HC (10 microg/mL) inhibited proliferation by up to 50%, with obvious apoptosis in some lines, and TGF-beta1 inhibited proliferation by more than 90%. Collagen production, as measured by [3H]proline incorporation or RIA for type III pro-collagen, was either unaffected or increased in the LDCs by HC. These divergent responses between LDC lines were partially explained by the absence of the glucocorticoid receptor (GR) and heat shock protein 90 mRNA in 10 of 12 LDC lines, but the presence of the mineralocorticoid receptor and 11beta-hydroxysteroid dehydrogenase type II. Western blot analysis confirmed the absence of the GR protein in cells lacking GR mRNA. Immunohistochemistry of human carotid lesions showed high levels of GR in the tunica media, but large areas lacking GR in the fibrous lesion. Considering the absence of the GR in most lines, the effects of HC may be elicited through the mineralocorticoid receptor. Functional resistance to the antiproliferative and antifibrotic effects of HC may contribute to excessive wound repair in atherosclerosis and restenosis.

Gene transfer of human prostacyclin synthase prevents neointimal formation after carotid balloon injury in rats

BACKGROUND AND PURPOSE

A disordered proliferative process in the vascular wall is thought to underlie the pathogenesis of restenosis after percutaneous transluminal angioplasty and carotid endarterectomy. A growth inhibitory property of overexpressed prostacyclin (PGI2) synthase (PGIS) was recently implicated in the pathological proliferation of vascular smooth muscle cells (VSMC) in vitro. Here, we investigated the effects of increased PGI2 synthesis on the pathological proliferation of VSMCs.

METHODS

The cDNA encoding human PGIS was transfected into endothelium-denuded rat carotid arteries after arterial balloon injury with the use of hemagglutinating virus Japan (HVJ). HVJ liposome vector complex without PGIS cDNA was used for vehicle control. The level of 6-keto PGF1alpha, a stable hydrolyzed metabolite of PGI2, the histological distribution of the immunoreactivity for human PGIS and the ratio of neointimal/medial area were analyzed.

RESULTS

In the analyses of 6-keto PGF1alpha, the level in the carotid arteries was significantly elevated 3 days after PGIS expression-vector transfection compared with that in the arteries after vehicle transfection. Seven days after human PGIS expression-vector transfection, the PGIS cDNA-transfected neointimal cells were strongly positive for human PGIS immunoreactivity in 81% sections examined. Fourteen days after the injury, the ratio of neointimal/medial area was 1.2+/-0.4 in the PGIS expression-vector transfected group, which was significantly smaller than that of the vehicle control group, 1.7+/-0.5; P<0.01.

CONCLUSIONS

It was thus demonstrated that the gene transfer of human PGIS expression-vector into rat carotid arteries resulted in the increased production of human PGI2 in the vascular wall, the expression of human PGIS in the developing neointima and significantly inhibited the neointimal formation generated after balloon injury.

MR microscopy of the arterial wall in an experimental model of atherosclerosis: preliminary results

PURPOSE

To obtain images of the arterial lumen and wall in a rabbit model of atherosclerosis with use of high-resolution magnetic resonance (MR) imaging to follow morphologic changes during the induction of atherosclerosis and, hence, develop a non-invasive tool to investigate restenosis.

MATERIALS AND METHODS

In vivo microscopic MR images of rabbit aorta were acquired after balloon injury. Measurements of wall and lumen diameter from MR images area were compared with measurements obtained from histologic and angiographic examination.

RESULTS

Injured rabbits exhibited an obvious thickening of the arterial wall, accompanied by an increased wall conspicuity, probably due to increases in T2. Quantitative MR morphometry corresponded well with morphologic measurements based on angiographic and histologic study.

CONCLUSIONS

MR implanted coil technology affords imaging of the arterial lumen and wall, allowing temporal assessment of the morphologic changes due to intimal hyperplasia after balloon dilation and may enable the evaluation of novel techniques to eliminate restenosis.

Syndecan-4 is a primary-response gene induced by basic fibroblast growth factor and arterial injury in vascular smooth muscle cells

Syndecans are a family of transmembrane proteoglycans that have been implicated in cell-extracellular matrix adhesion and growth factor binding. We reported previously that syndecan-1 expression by cultured rate vascular smooth muscle cells (VSMCs) is induced by serum- or platelet-derived growth factor (PDGF). We now report that syndecan-4 mRNA is rapidly induced in cultured VSMCs in response to basic fibroblast growth factor (bFGF) or serum stimulation. In the presence of cycloheximide, induction of syndecan-4 mRNA was enhanced. These characteristics identified syndecan-4 as a primary-response gene product in VSMCs. In contrast, syndecan-1 mRNA expression in response to serum was completely blocked in the presence of cycloheximide. We also examined the expression of syndecan mRNAs in VSMCs in response to balloon catheter injury in vivo. A reverse transcriptase-polymerase chain reaction technique was developed that enabled us to amplify all four syndecan mRNAs in a single reaction tube and determine relative changes in their expression. All four syndecan mRNAs were detected in uninjured rat carotid arteries. In endothelium-denuded arteries, the medial layer (presumably VSMCs) accounted for 70% to 90% of the syndecan mRNAs in the vessel wall. The levels of syndecan-2 and syndecan-3 mRNAs were not altered significantly after balloon injury. In contrast, syndecan-4 mRNA was increased at early times after injury but then decreased to control level by 7 days. Syndecan-1 mRNA levels showed a slower but prolonged increase that reached a maximum at 7 days after injury. Immunostaining with anti-syndecan-4 antibodies demonstrated a rapid increase in syndecan-4 proteoglycan expression in the injured carotid artery.

Activated transcription factor nuclear factor-kappa B is present in the atherosclerotic lesion

Nuclear factor-kappa B (NF-kappaB)/Rel transcription factors play an important role in the inducible regulation of a variety of genes involved in the inflammatory and proliferative responses of cells. The present study was designed to elucidate the implication of NF-kappaB/Rel in the pathogenesis of atherosclerosis. Activation of the dimeric NF-kappaB complex is regulated at a posttranslational level and requires the release of the inhibitor protein IkappaB. The newly developed mAb alpha-p65mAb recognizes the IkappaB binding region on the p65 (RelA) DNA binding subunit and therefore selectively reacts with p65 in activated NF-kappaB. Using immunofluorescence and immunohistochemical techniques, activated NF-kappaB was detected in the fibrotic-thickened intima/media and atheromatous areas of the atherosclerotic lesion. Activation of NF-kappaB was identified in smooth muscle cells, macrophages, and endothelial cells. Little or no activated NF-kappaB was detected in vessels lacking atherosclerosis. Electrophoretic mobility shift assays and colocalization of activated NF-kappaB with NF-kappaB target gene expression suggest functional implications for this transcription factor in the atherosclerotic lesion. This study demonstrates the presence of activated NF-kappaB in human atherosclerotic tissue for the first time. Atherosclerosis, characterized by features of chronic inflammation and proliferative processes, may be a paradigm for the involvement of NF-kappaB/Rel in chronic inflammatory disease.

Structure of the 5'-flanking regulatory region of the mouse gene encoding the clearance receptor for atrial natriuretic peptide

A full-length cDNA, encoding the mouse atrial natriuretic peptide clearance receptor (ANP-CR), was isolated from a mouse lung cDNA library. The deduced amino acid sequence of the mouse ANP-CR, showing a typical tripartite organization which lacks a guanylyl cyclase domain, was extremely well conserved compared with the ANP-CR homologs. To understand the molecular mechanisms underlying the regulation of mouse ANP-CR gene expression and to define the essential DNA sequences for the transcriptional activity, a genomic clone containing over 9 kb of the 5'-flanking region of the mouse ANP-CR gene has been isolated from a mouse genomic library. Sequence analysis revealed that the 2.3-kb region upstream from an ATG codon of the mouse ANP-CR gene contained a number of putative regulatory elements; TATA box, CAAT box, cAMP response element, AP-1 and two shear stress responsive elements. Additionally, an unusual feature was the presence of the tandem-repeated AP-2-like elements, which were closely overlapped with SP-1 element. Promoter analysis using deletion plasmids in mouse Balb/3T3 cells, highly producing ANP-CR mRNA, demonstrated that deletion of the sequence from -144 to +46 relative to the transcription start point caused a dramatic decrease of the transcriptional activity and that the TATA box at -269 was not essential for the basal transcriptional activity. Primer extension analysis indicated that transcription of the mouse ANP-CR gene starts from at least two major sites, suggesting that the sequence from -144 to +46, which was shown to involve a novel sequence composed of tandem-repeated TATA-box-like elements, contained promoter sequences. Furthermore, cis-acting negative elements were shown to be situated in three regions (from -1178 to -708, from -707 to -625 and from -248 to -145) of the mouse ANP-CR gene promoter.

Migration behavior of human smooth muscle cells cultivated from restenotic and primary lesions

Subintimal smooth muscle cell (SMC) migration is considered an essential determinant of arteriosclerosis and neointimal formation. In this study, a cell culture model was established to characterize migration activity of SMCs originating from restenotic and primary lesions. Plaques from symptomatic stenoses of 32 patients (19 men, 13 women; 4 carotid, 17 peripheral, 11 coronary lesions) were removed by percutaneous atherectomy or direct operative approach. Ten patients suffered from recurrent stenosis. Cell cultures were established by explantation of tissue samples. By indirect immunofluorescence microscopy, SMCs were shown to be the predominant cell type of all advanced lesions irrespective of their origin. The spontaneous cellular motility of SMCs was analyzed in vitro by means of a computer-assisted observation system. Cells of all groups exhibited random motility. SMC migratory velocity was found to be significantly (P < 0.001) greater in cells from restenotic lesions than in those from primary plaques. In conclusion, migration behavior of human SMCs originating from arteriosclerotic lesions may be quantified in vitro as a functional determinant characterizing restenotic versus primary lesions.

The influence of surgical insults on restenosis after transluminal balloon angioplasty

The influences of atherogenic response on restenosis after transluminal balloon angioplasty and the anastomosis of arterial reconstruction were investigated. Iliac transluminal balloon angioplasty was performed on 81 consecutive patients at 86 sites, between January, 1987 and December, 1992. A balloon angioplasty alone was performed in 58 patients at 60 sites, while distal revascularization was performed in 23 patients on 26 limbs, in association with the angioplasty. An improvement in the inflow of the distal grafts was achieved in 22 of these 23 patients in 26 limbs. The combined distal revascularization included 21 femoropopliteal bypasses, 3 femorofemoral bypasses, and 2 thromboendarterectomies at the profunda femoris arteries. A reduction in the luminal diameter after the balloon angioplasty was determined by means of follow-up arteriograms which showed no obvious progression of the restenosis at the angioplasty sites even when neointimal hyperplasia had developed at the anastomosis of the arterial reconstruction. The accumulative graft patency rate of the combined distal revascularization did not differ significantly from that of femoropopliteal reconstructions alone during the same study period. This study demonstrated that concomitant surgical insults do not have a detrimental effect on restenoses at angioplasty sites.

A definition of advanced types of atherosclerotic lesions and a histological classification of atherosclerosis. A report from the Committee on Vascular Lesions of the Council on Arteriosclerosis, American Heart Association

This report is the continuation of two earlier reports that defined human arterial intima and precursors of advanced atherosclerotic lesions in humans. This report describes the characteristic components and pathogenic mechanisms of the various advanced atherosclerotic lesions. These, with the earlier definitions of precursor lesions, led to the histological classification of human atherosclerotic lesions found in the second part of this report. The Committee on Vascular Lesions also attempted to correlate the appearance of lesions noted in clinical imaging studies with histological lesion types and corresponding clinical syndromes. In the histological classification, lesions are designated by Roman numerals, which indicate the usual sequence of lesion progression. The initial (type 1) lesion contains enough atherogenic lipoprotein to elicit an increase in macrophages and formation of scattered macrophage foam cells. As in subsequent lesion types, the changes are more marked in locations of arteries with adaptive intimal thickening. (Adaptive thickenings, which are present at constant locations in everyone from birth, do not obstruct the lumen and represent adaptations to local mechanical forces). Type II lesions consist primarily of layers of macrophage foam cells and lipid-laden smooth muscle cells and include lesions grossly designated as fatty streaks. Type III is the intermediate stage between type II and type IV (atheroma, a lesion that is potentially symptom-producing). In addition to the lipid-laden cells of type II, type III lesions contain scattered collections of extracellular lipid droplets and particles that disrupt the coherence of some intimal smooth muscle cells. This extracellular lipid is the immediate precursor of the larger, confluent, and more disruptive core of extracellular lipid that characterizes type IV lesions. Beginning around the fourth decade of life, lesions that usually have a lipid core may also contain thick layers of fibrous connective tissue (type V lesion) and/or fissure, hematoma, and thrombus (type VI lesion). Some type V lesions are largely calcified (type Vb), and some consist mainly of fibrous connective tissue and little or no accumulated lipid or calcium (type Vc).

A definition of advanced types of atherosclerotic lesions and a histological classification of atherosclerosis. A report from the Committee on Vascular Lesions of the Council on Arteriosclerosis, American Heart Association

This report is the continuation of two earlier reports that defined human arterial intima and precursors of advanced atherosclerotic lesions in humans. This report describes the characteristic components and pathogenic mechanisms of the various advanced atherosclerotic lesions. These, with the earlier definitions of precursor lesions, led to the histological classification of human atherosclerotic lesions found in the second part of this report. The Committee on Vascular Lesions also attempted to correlate the appearance of lesions noted in clinical imaging studies with histological lesion types and corresponding clinical syndromes. In the histological classification, lesions are designated by Roman numerals, which indicate the usual sequence of lesions progression. The initial (type I) lesion contains enough atherogenic lipoprotein to elicit an increase in macrophages and formation of scattered macrophage foam cells. As in subsequent lesion types, the changes are more marked in locations of arteries with adaptive intimal thickening. (Adaptive thickenings, which are present at constant locations in everyone from birth, do not obstruct the lumen and represent adaptations to local mechanical forces). Type II lesions consist primarily of layers of macrophage foam cells and lipid-laden smooth muscle cells and include lesions grossly designated as fatty streaks. Type III is the intermediate stage between type II and type IV (atheroma, a lesion that is potentially symptom-producing). In addition to the lipid-laden cells of type II, type III lesions contain scattered collections of extracellular lipid droplets and particles that disrupt the coherence of some intimal smooth muscle cells. This extracellular lipid is the immediate precursor of the larger, confluent, and more disruptive core of extracellular lipid that characterizes type IV lesions. Beginning around the fourth decade of life, lesions that usually have a lipid core may also contain thick layers of fibrous connective tissue (type V lesion) and/or fissure, hematoma, and thrombus (type VI lesion). Some type V lesions are largely calcified (type Vb), and some consist mainly of fibrous connective tissue and little or no accumulated lipid or calcium (type Vc).

Effect of nonanticoagulant heparin (Astenose) on restenosis after balloon angioplasty in the atherosclerotic rabbit

PURPOSE

To determine whether intravenous administration of Astenose, a high-molecular-weight nonanticoagulant heparin, can reduce restenosis following balloon angioplasty in a rabbit model.

MATERIALS AND METHODS

Focal atherosclerosis was induced in 54 rabbits (89 vessel), and angioplasty was performed after animals were randomized into five groups. Group 1 vessels (control) were treated with lactated Ringer solution for 28 days (n = 19); group 2, Astenose at 0.10 mg/kg per hour for 28 days (n = 16); group 3, Astenose at 0.33 mg/kg per hour for 28 days (n = 16); group 4, Astenose at 0.60 mg/kg per hour for 28 days (n = 17); and group 5, Astenose at 0.33 mg/kg per hour for 14 days (n = 21). Arteriograms were obtained to measure minimal luminal diameters before, immediately after, and 28 days after angioplasty, and the rabbits were killed for histologic analysis.

RESULTS

Angiographically demonstrated restenosis was significantly reduced in groups 3 (18.9% +/- 3.7, P = .04) and 4 (20.2% +/- 3.1, P = .04) compared with the control group (32.4% +/- 4.8). Group 5 showed a nonsignificant trend toward reduced restenosis (23.1% +/- 2.9, P = .09), and group 2 showed restenosis similar to that in group 1 (31.0% +/- 2.5, P = .80). However, quantitative histopathologic analysis detected no differences among the groups in absolute plaque area. Medial area was significantly smaller in groups 2 and 5 (P < or = .002) than in group 1, and there was a nonsignificant trend toward reduced medial area in groups 3 and 4 (P = .12).

CONCLUSION

Long-term intravenous Astenose therapy resulted in a modest but statistically significant reduction in angiographically demonstrated restenosis after angioplasty in this atherosclerotic rabbit model.

Taxol inhibits neointimal smooth muscle cell accumulation after angioplasty in the rat

Despite significant improvements in the primary success rate of the medical and surgical treatments for atherosclerotic disease, including angioplasty, bypass grafting, and endarterectomy, secondary failure due to late restenosis continues to occur in 30-50% of individuals. Restenosis and the later stages in atherosclerotic lesions are due to a complex series of fibroproliferative responses to vascular injury involving potent growth-regulatory molecules (such as platelet-derived growth factor and basic fibroblast growth factor) and resulting in vascular smooth muscle cell (VSMC) proliferation, migration, and neointimal accumulation. We show here, based on experiments with both taxol and deuterium oxide, that microtubules are necessary for VSMCs to undergo the multiple transformations contributing to the development of the neointimal fibroproliferative lesion. Taxol was found to interfere both with platelet-derived growth factor-stimulated VSMC migration and with VSMC migration and with VSMC proliferation, at nanomolar levels in vitro. In vivo, taxol prevented medial VSMC proliferation and the neointimal VSMC accumulation in the rat carotid artery after balloon dilatation and endothelial denudation injury. This effect occurred at plasma levels approximately two orders of magnitude lower than that used clinically to treat human malignancy (peak levels achieved in this model were approximately 50-60 nM). Taxol may therefore be of therapeutic value in preventing human restenosis with minimal toxicity.

Specific inhibition of eIF-5A and collagen hydroxylation by a single agent. Antiproliferative and fibrosuppressive effects on smooth muscle cells from human coronary arteries

Restenosis occurs in 35% of patients within months after balloon angioplasty, due to a fibroproliferative response to vascular injury. These studies describe a combined fibrosuppressive/antiproliferative strategy on smooth muscle cells cultured from human primary atherosclerotic and restenotic coronary arteries and from normal rat aortas. L-Mimosine suppressed the posttranslational hydroxylation of the precursors for collagen and for eukaryotic initiation factor-5A (eIF-5A) by directly inhibiting the specific protein hydroxylases involved, prolyl 4-hydroxylase (E.C. 1.14.11.2) and deoxyhypusyl hydroxylase (E.C. 1.14.99.29), respectively. Inhibition of deoxyhypusyl hydroxylation correlated with a dose-dependent inhibition of DNA synthesis. Inhibition of prolyl hydroxylation caused a dose-dependent reduction in the secretion of hydroxyproline-containing protein and decreased the formation of procollagen types I and III. The antifibroproliferative action could not be attributed to nonspecific or toxic effects of mimosine, appeared to be selective for the hydroxylation step in the biosynthesis of the procollagens and of eIF-5A, and was reversible upon removal of the compound. The strategy of targeting these two protein hydroxylases has important implications for the pathophysiology of restenosis and for the development of agents to control fibroproliferative diseases.

Omega-3 fatty acids in smooth muscle cell phospholipids increase membrane cholesterol efflux

The aim of our work was to determine whether fatty acid modifications in smooth muscle cell phospholipids affect cholesterol efflux and desorption. [3H]Cholesterol was used to label cholesterol pools in the whole cell or selectively in the plasma membrane. Cells were incubated for 12 h in order to increase oleate, linoleate, arachidonate, eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) in phospholipids. Cholesterol efflux was monitored using native or tetranitromethane modified high-density lipoprotein3 (HDL3). When all cholesterol pools were labeled, the efflux from cells treated with different fatty acids were not different. Plasma membrane cholesterol efflux remained unchanged after oleate, linoleate or arachidonate treatments, but was markedly increased after EPA and DHA enrichment, both with native HDL3 and with tetranitromethane-high-density lipoprotein. These results suggest that the positive effects of n-3 fatty acid consumption on the atherosclerotic process could be linked in part to an increase in plasma membrane cholesterol efflux from vascular smooth muscle cells.

Decrease in high density lipoprotein binding sites is associated with decrease in intracellular cholesterol efflux in dedifferentiated aortic smooth muscle cells

One of the key features of atherosclerosis formation and progression is 'dedifferentiation' of contractile arterial smooth muscle cells (SMC) in synthetic cells. In primary cultures and subcultures before 10 and after 200 passages, SMC exhibit contractile-like, synthetic and transformed phenotypes, respectively, providing a good model for studying dedifferentiation process in vitro: the rationale for comparing these phenotypes of SMC in vivo rests in similar changes in cytoenzymatic and cytoskeletal features. In vivo, dedifferentiated SMC are transformed into foam cells by accumulating lipids. Thus, the aim of this study was to determine whether cholesterol metabolism undergoes changes in dedifferentiated cells and the three cultured phenotypes were compared in regard to their cholesterol efflux mechanisms. Phenotypic changes were shown to be associated with decrease in intracellular cholesterol apoprotein mediated efflux and translocation but also with decrease in high affinity binding sites for native HDL. Thus, the dedifferentiation process triggers a need for increased supply of cholesterol for membrane synthesis and efflux down-regulation mechanisms are aimed at maximizing cholesterol availability to the cell. Plasma membrane cholesterol efflux, which seems to be apoprotein-independent, decrease slightly with cell dedifferentiation suggesting either modifications in the dedifferentiated cell membranes physical properties. Taken together, these different results showed that dedifferentiation of arterial SMC is associated with decrease in the different steps of the efflux process, which could constitute one of the early events in their foam cell transformation.

Molecular and cellular concepts in atherosclerosis

Atherosclerosis is a complex disease of uncertain cause. Its pathobiology is believed to represent an abnormal expression of the processes of vascular healing. Etiologic models derive from a 'response to injury' paradigm and can be divided into three separate disease stages: endothelial dysfunction, smooth muscle proliferation and architectural disruption. The initiating event of endothelial dysfunction is unknown, but is believed to be related to low-density lipoproteins and/or their oxidized derivatives. Endothelial injury is signalled to the smooth muscle cells of the media by three routes: direct cell-cell interaction, secretion of soluble growth factors and monocyte-derived cytokines. Monocytes are recruited by the endothelium and invade the subintimal space by a complex interaction of a variety of adhesion proteins and receptors on both cell types. Smooth muscle cell proliferation is initiated by a change in phenotype expression from 'contractile' to 'synthetic' resulting from the binding of fibronectin to specific integrin receptors. Three functionally distinct activities may represent separate subtypes of the 'synthetic phenotype': migration from the media to the intima, increased proliferation and inappropriate extracellular matrix synthesis. The loss of normal regulatory control and anchorage independence of proliferation suggest a relationship to oncogenic transformation. Both migration and proliferation result from the binding of platelet-derived growth factor-like factors to smooth muscle cell receptors, which initiates a cascade of intracellular molecular events leading either to cytoskeletal locomotory restructuring or cell cycle activation. Both pathways also appear to be coregulated by integrin receptors and both depend upon phosphorylation of cell membrane, cytosolic and nuclear regulatory proteins. Clinical expression of atherosclerosis may follow sudden loss of architectural integrity of the intimal plaque by three different mechanisms: plaque fissuring, intraluminal plaque rupture or intramural hemorrhage related to abnormal vessel wall stress and/or biochemistry.

Analysis of atherectomy specimens

Atherectomy specimens may be regarded as biopsy tissue excised from human vascular target lesions. Proceeding from contrary histologic findings that attribute focal hypercellularity to restenosis, and hypocellularity to chronic lesions, further analysis of atherectomy specimens was performed to study ultrastructural characteristics and functional aspects propagated by both lesion types. Transmission electron microscopy examination showed that intimal smooth muscle cells (SMCs) were the predominant cells in both primary and restenotic lesions. SMCs exhibited variable degrees of metabolic activation, typically higher in SMCs of restenotic lesions. This SMC phenotype was equally expressed when tissue samples were placed in a cell culture model. In an attempt to quantify SMC activity, proliferative as well as migratory activities of cultured cells were measured by growth curves and a computer-assisted motion analysis system, respectively. A 2- to 3-fold increase of both activity determinants was observed with SMCs cultivated from restenotic lesions compared with those from primary lesions, irrespective of their coronary or peripheral origin. Drug-induced interference of human SMC metabolic activation and antagonism to their proliferative and migratory activities may be helpful in evaluation of therapeutic concepts to prevent restenosis. The antitubulin colchicine was studied for its effect on the defined determinants. The data in vitro demonstrate that colchicine decreased proliferative and migratory activity of SMCs and caused disorganization of the cytoplasmic ultrastructure. In conclusion, electron microscopy and cell culture studies may help to shed more light on the structures and mechanisms underlying restenosis and plaque growth. Deliberate counteraction of any of the specific early events implicated in these complex pathobiologic processes may eventually become effective means to suppress restenosis and may thus result in a prophylactic as well as therapeutic treatment of the diseased vascular wall.

The pathogenesis of atherosclerosis: a perspective for the 1990s

Atherosclerosis, the principal cause of heart attack, stroke and gangrene of the extremities, is responsible for 50% of all mortality in the USA, Europe and Japan. The lesions result from an excessive, inflammatory-fibroproliferative response to various forms of insult to the endothelium and smooth muscle of the artery wall. A large number of growth factors, cytokines and vasoregulatory molecules participate in this process. Our ability to control the expression of genes encoding these molecules and to target specific cell types provides opportunities to develop new diagnostic and therapeutic agents to induce the regression of the lesions and, possibly, to prevent their formation.

Frequency and consequences of intimal hyperplasia in specimens retrieved by directional atherectomy of native primary coronary artery stenoses and subsequent restenoses

Although intimal hyperplasia is a frequent occurrence after arterial interventional procedures, the overall frequency and significance of intimal hyperplasia in primary coronary lesions has not been previously addressed. The incidence of intimal hyperplasia was therefore examined using standard light microscopy in specimens obtained from native coronary arteries of patients undergoing directional coronary atherectomy. The associated clinical history, angiographic results and clinical outcomes were also tabulated. Intimal hyperplasia was identified in 51 of 55 patients (93%) treated with directional coronary atherectomy for restenosis after a prior intervention. These restenosis lesions had less acute gain in lumen diameter after directional coronary atherectomy, a smaller late lumen diameter, more severe late stenosis (p < 0.04), and tended to have more restenosis defined as late stenosis > or = 50% (restenosis rate 40% for prior restenosis vs 26% for primary lesions). Surprisingly, however, intimal hyperplasia was also identified in 45 of 102 (44%) primary stenoses. Primary lesions (n = 45) with intimal hyperplasia were more likely to occur in younger patients and in the left anterior descending artery than were either primary lesions without intimal hyperplasia (n = 57) or prior restenosis lesions. There were otherwise no differences in the baseline characteristics, angiographic findings or clinical outcome of primary lesions with or without intimal hyperplasia (restenosis rate 28 and 24%, respectively). The event-free survival (72% at 12 months) was similar in all 3 groups. Thus, even though intimal hyperplasia is an almost universal finding in restenosis lesions, intimal hyperplasia is not specific for restenosis since histologically identical hyperplasia may be found in nearly half of primary coronary artery stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Composition and classification of human atherosclerotic lesions

Human atherosclerotic disease can be resolved into eight types of lesion, each characterized by its composition and structure and the absence or degree of intimal injury. The eight types have been arranged in the sequence in which they may progress in complexity from the initial change in childhood or youth to the clinical endpoints in older persons. While lesions at first increase primarily by intra- and extracellular accumulation of lipid, this in itself rarely accounts for symptomatic obstruction. Lipidic lesions become symptomatic primarily by means of successively superimposed deposits of thrombotic material. Non-homogeneity of hemodynamic forces within the length of an artery account for local differences in intima thickness (adaptive intimal thickening) and, in persons with risk factors, differences in susceptibility to lesion formation. According to the degree to which they can accumulate or retain lipid and bring about secondary mechanisms, specific locations of the arterial tree have been designated as atherosclerosis-resistant, atherosclerosis-prone and progression-prone.

Fucoidan is a non-anticoagulant inhibitor of intimal hyperplasia

We previously reported that heparin inhibits the proliferation of fibroblasts and vascular smooth muscle cells (SMC), in part, by binding to and increasing the antiproliferative activity of transforming growth factor-beta 1 (TGF-beta 1). We now report that certain other polyanions which are structurally distinct from heparin, such as fucoidan and polyinosinic acid, are more avid ligands for TGF-beta 1 and more potent antiproliferative agents than heparin. Fucoidan possessed more potent antiproliferative activity than heparin against rat and bovine aortic SMC in vitro, though possessing much lower anticoagulant activity than heparin. Furthermore, fucoidan suppressed in vivo intimal hyperplasia when continuously infused into rats subjected to balloon-catheter injury. Unlike heparin, which also suppressed intimal hyperplasia, fucoidan did not cause systemic anticoagulation. Thus, fucoidan may be useful as a non-anticoagulant inhibitor of post-angioplasty intimal hyperplasia.

Platelet-derived growth factor promotes smooth muscle migration and intimal thickening in a rat model of balloon angioplasty

Platelet-derived growth factor (PDGF) is a mitogen and chemoattractant for vascular smooth muscle cells (SMC) in vitro, but its activities in vivo remain largely undefined. We infused recombinant PDGF-BB (0.01-0.30 mg/kg per d i.v.) into rats subjected to carotid injury. PDGF-BB produced a small increase (two- to threefold) in medial SMC proliferation. More importantly, PDGF-BB greatly increased (20-fold) the intimal thickening and the migration of SMC from the media to the intima during the first 7 d after injury. These data provide support for the hypothesis that PDGF, and perhaps other platelet factors, might play an important role in the movement of mesenchymal cells into zones of injury undergoing repair.

Migratory activity of human smooth muscle cells cultivated from coronary and peripheral primary and restenotic lesions removed by percutaneous atherectomy

BACKGROUND

The successful cultivation of human smooth muscle cells (SMC) from coronary and peripheral atherosclerotic lesions removed by percutaneous directional atherectomy is described.

METHODS AND RESULTS

Sixty-seven patients in whom plaque material was obtained compose the study population. A total of 73 lesions from both coronary (n = 38) and peripheral (n = 35) arteries of primary (n = 50) and restenotic origin (n = 23) were studied. Successful cultivation was significantly (p less than 0.001) dependent on the quantity of plaque material submitted. Fifty-five percent of patients in whom atherectomy specimens were removed from coronary lesions yielded an adequate SMC population in comparison to 89% of those from peripheral arteries (p less than 0.01). Cultivation was not dependent on the age and sex of patients, lesion origin, risk factors, medications, or incidence of unstable angina. In an attempt to quantify SMC activity, migratory velocity was measured with a computer-assisted motion analysis system. SMC migratory velocity was found to be significantly (p less than 0.001) greater in restenotic than in primary plaque material. This finding was confirmed for both coronary and peripheral lesions.

CONCLUSIONS

Our data suggest that elevated SMC migratory activity may be an important mechanism in the development of restenotic lesions.

Quantitative angiography after directional coronary atherectomy

OBJECTIVE

To assess by quantitative analysis the immediate angiographic results of directional coronary atherectomy. To compare the effects of successful atherectomy with those of successful balloon dilatation in a series of patients with matched lesions.

DESIGN

Case series.

SETTING

Tertiary referral centre.

PATIENTS

62 patients in whom directional coronary atherectomy was attempted between 7 September 1989 and 31 December 1990.

INTERVENTIONS

Directional coronary atherectomy.

MAIN OUTCOME MEASURES

Increase in minimal luminal diameter of coronary artery segment.

RESULTS

Angiographic success on the basis of intention to treat was obtained in 54 patients (87%). In four patients the lesion could not be crossed by the atherectomy device; all four had an uneventful conventional balloon angioplasty. Four of the 58 patients who underwent atherectomy were subsequently referred for coronary bypass surgery because of failure or complications; three of them sustained a transmural infarction. In the successful cases, coronary atherectomy resulted in an increase in the minimal luminal diameter from 1.1 mm to 2.5 mm with a concomitant decrease of the diameter stenosis from 62% to 22%. In the subset of 37 patients in which the changes induced were compared with conventional balloon angioplasty atherectomy increased the minimal luminal diameter more than balloon angioplasty (1.6 v 0.8 mm; p less than 0.0001). Conventional histology showed media or adventitia in 26% of the atherectomy specimens. In hospital complications occurred in six patients who had undergone a successful procedure: two transmural infarctions, two subendocardial infarctions, one transient ischaemia attack, and one death due to delayed rupture of the atherectomised vessel. All patients were clinically evaluated at one and six months. One patient had persisting angina (New York Heart Association class II), one patient sustained a myocardial infarction, one patient underwent a percutaneous transluminal coronary angioplasty for early restenosis, and one patient underwent coronary bypass surgery because of a coronary aneurysm formation. At six months 80% (36/47) of the patients were symptom free.

CONCLUSIONS

Coronary atherectomy achieved a better immediate angiographic result than balloon angioplasty; however, in view of the complication rate in this preliminary series, which may be related to a learning curve, a randomised study is needed to show whether this procedure is as safe as a conventional balloon angioplasty.

Pharmacologic roles of heparin and glucocorticoids to prevent restenosis after coronary angioplasty

Restenosis after successful percutaneous transluminal coronary angioplasty is the major clinical problem limiting the long-term efficacy of this treatment for coronary atherosclerosis. Recent advances in the understanding of the biology of restenosis indicate that intimal hyperplasia of smooth muscle cells is the predominant cause for restenosis. Therefore, therapeutic agents that inhibit vascular smooth muscle cell proliferation should be candidate drugs to prevent restenosis. Heparin has documented antiproliferative effects on smooth muscle cells, and the availability of low molecular weight heparins that lack anticoagulant properties makes them ideal agents. Glucocorticoids have wide effects on inflammatory and wound healing events and inhibit smooth muscle cell growth in culture and in animal models of arterial injury. Recent laboratory data suggest that combination therapy with both low molecular weight heparin and hydrocortisone may be a powerful treatment regimen to limit restenosis.

Cell culture systems to study progression and inhibition of intimal proliferations

Vascular smooth muscle cells, endothelial cells, and fibroblasts are the main cellular constituents of artery walls. Mass cultures and clone cultures of these cell types have meanwhile become valuable tools in the research of the genesis, pathophysiology, and therapy of vessel-wall diseases. With transfilter co-culture systems the three-layered construction of the artery wall can be imitated in vitro, and it has become possible to induce smooth muscle cell proliferates in these in vitro system which resemble, in many respects, intimal proliferates as they often occur after angioplasty, stent- or bypass operations in the form of secondary stenoses. With this technique the interaction of the three cell species of artery walls can be easily studied. The time-course of the development of smooth muscle cell proliferates in vitro resembles the in vivo scenario. Addition of oxidized lipoproteins and monocytes to the culture medium of transfilter cultures leads to atheroma-like proliferates. Culturing whole artery segments is another in vitro technique for induction of intimal proliferates, and enables the production of intimal proliferates in a way similar to transfilter culture systems. Because of the striking similarities of the cellular responses of transfilter- and organ-culture systems with in vivo processes in atherogenesis, and in the development of secondary stenoses after angioplasty, the described co-culture systems are suitable for studying the genesis, pathophysiology, and therapy of stenosing artery processes, as well as to obtain further insight into basic problems of cell interaction in vessel walls.

In vitro growth characteristics of human atherosclerotic plaque cells: comparison of cells from primary stenosing and restenosing lesions of peripheral and coronary arteries

Cell size distribution and growth rates were studied in vitro in human plaque cells from advanced primary stenosing and fresh restenosing lesions of peripheral and coronary arteries. Cells were isolated either by the explant technique or by enzymatic disaggregation and were identified as smooth muscle cells by their typical growth pattern and their positive reaction with antibodies against smooth muscle alpha-actin. Endothelial cells were found in plaque specimens from coronary arteries but were only present in primary cultures. Smooth muscle cells from primary stenosing tissue (ps-SMC) exhibited a significantly lower growth rate in culture (0.15 +/- 0.04 population doublings per day; means +/- SD) compared with cells from restenosing lesions (re-SMC; 0.60 +/- 0.13 population doublings per day; means +/- SD). ps-SMC usually became senescent in their second passage, i.e., after 5-7 cumultive population doublings. re-SMC retained their high proliferative activity even after five passages (15 cumulative population doublings). Cell populations of both origins consisted of two distinct subpopulations which could be discriminated by cell size measurements: relatively small, predominant cells (cell diameter: 18.0 +/- 4 microns; means +/- SD) and large fibroblast-like cells (cell diameter: 26.0 +/- 3 microns; means +/- SD). The proportion of large cells was higher in cell populations derived from primary stenosing tissue. These results suggest that stenosing plaque tissue from human peripheral and coronary arteries consists of two smooth muscle cell subpopulations. The low proliferative activity of total smooth muscle cell populations of advanced primary stenosing lesions contrasts with the high mitotic activity of smooth muscle cells obtained from secondary stenosing intimal proliferates.

Differential effect of Photofrin II on growth of human smooth muscle cells from nonatherosclerotic arteries and atheromatous plaques in vitro

The effect of dihematoporphyrin-ester or -ether (DHE), a photosensitizing porphyrin with different amounts of aggregates, on the growth of cultured smooth muscle cells obtained from nonatherosclerotic arteries and from atheromatous plaques (primary stenosing and restenosing lesions) was examined without photoactivation of the drug. Clinically relevant DHE concentrations ranging from 0.1 to 25 micrograms/ml were used. In all proliferation studies with cells of second and third passage (approximately 10 cumulative population doublings in vitro), the growth rates decreased in a dose-dependent manner. Smooth muscle cells from atherosclerotic lesions were significantly more sensitive than smooth muscle cells from normal arteries. Cells derived from restenosing lesions retained their increased sensitivity even after eight passages in culture (approximately 20 cumulative population doublings). Cell size measurements showed that the decreased proliferative activity mainly occurred in smooth muscle cell subpopulations consisting of small cells. A cytotoxic effect of DHE was observed at concentrations above 5 micrograms/ml, causing cytoplasmic protrusions, vacuoles, and even complete cell lysis. At a DHE concentration of 5 micrograms/ml, the number of viable cells was 73% +/- 14% (means +/- SD) for smooth muscle cells from nonatherosclerotic arterial media and only 38% +/- 11% (means +/- SD) for smooth muscle cells from atherosclerotic plaques. In all experiments, no significant difference in response to DHE treatment was observed between cells from primary stenosing and restenosing lesions, suggesting a specific mechanism for plaque-derived cells causing an increased sensitivity in comparison to smooth muscle cells from nonatherosclerotic arteries. The pronounced sensitivity of plaque cells against DHE treatment suggests that this drug--even without photoactivation--is potentially valuable in vivo as a therapeutic approach to vascular stenoses.

Responses of cultured smooth muscle cells from human nonatherosclerotic arteries and primary stenosing lesions after photoradiation: implications for photodynamic therapy of vascular stenoses

Cultured smooth muscle cells from human nonatherosclerotic arteries and from primary stenosing lesions were labeled with dihematoporphyrinester and ether, a photosensitizing probe used mainly for the detection and photodynamic therapy of tumors. After labeling for 24 h, cells were irradiated with ultraviolet light (wavelength 365 nm, energy densities ranging from 30 to 1,200 mJ/cm2). Twenty-four hours after photoradiation, 80% of smooth muscle cells from nonatherosclerotic arteries and only 20% of smooth muscle cells from atherosclerotic plaques were viable and still adherent. Moreover, dynamic cell and cytoskeletal alterations in response to irradiation are described. The differential sensitivity of smooth muscle cells from nonatherosclerotic arteries and from atherosclerotic plaques provides evidence that a photodynamic treatment might be a valuable therapeutic approach to vascular stenosis.